The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In previously developed energy harvesting systems, an electrical output signal from an energy harvesting device or component is often used to power the components of electrical circuitry that generate a useable (typically an oscillating) output signal. The useable output signal may then be used for various purposes, such as to power other devices requiring electrical power for their operation.
In some instances the electrical circuitry used to receive the output from the energy harvesting device involves one or more metal oxide silicon field effect transistors (MOSFETs) or other similar, semiconductor switching devices. Such switching devices require a certain forward bias voltage to be switched on. This arrangement has significant drawbacks from an efficiency standpoint. This is because a significant percentage of the output from the energy harvesting device must often be used as the biasing current to turn on and off the semiconductor switching devices. This portion of the output from the energy harvesting device is thus effectively “lost” and the output power available from the system is reduced accordingly. Put differently, the need to use a portion of the output from the energy harvesting device to power various electrical switching components (i.e., components that are needed to produce a useable electrical output signal), reduces the overall efficiency of the energy harvesting system.
In many applications, there is more than one available source of energy, which might be termed a “secondary” source of energy, that can be harvested. However, the secondary energy source, standing alone, might not yield sufficient electrical power for the specific application that energy harvesting is contemplated for, and therefore no attempt is made to harvest the small amount of energy from the secondary source.